Thank you for the help. I manage to figure it out

Depends on what worksheet data means exactly.

If you're talking about the fields defined within a worksheet, you'll have to go for ir.model.fields. If you're after the actual data entered into such a worksheet, you have to go for 'that worksheet model'.

A working example for both cases:

import xmlrpc.client

url = 'https://subdomain.odoo.com'
db = 'dbname'
username = 'username'
password = 'password'

# Worksheet Templates are defined on Projects (project.project) 
#  and can be overridden on Tasks (project.task).
#  Below example just goes by the task, but the same concept can 
#  be applied to project.project worksheet_template_id as well.
_task_id = 42

# Authentication
common = xmlrpc.client.ServerProxy('{}/xmlrpc/2/common'.format(url))
uid = common.authenticate(db, username, password, {})
models = xmlrpc.client.ServerProxy('{}/xmlrpc/2/object'.format(url))

# optional: perform additional search within the known task(s)
task_id = models.execute_kw(db, uid, password, 'project.task', 'search', [[['id', '=', _task_id]]])
print(f'task_id: {task_id}')
# result: 
#  task_id: [42]

# read the task data and receive 'fields' - here we're interested 
#  in the worksheet_template_id assigned to that task:
tasks = models.execute_kw(db, uid, password, 'project.task', 'read', [task_id], {'fields': ['worksheet_template_id']})
print(f'tasks: {tasks}')
# result: 
#  tasks: [{'id': 42, 'worksheet_template_id': 
#          [1, 'Default Worksheet']}]

# optional: perform additional search within the known worksheet 
#  templates; in case you've been searching for multiple tasks 
#  and have receveived multiple worksheet templates. at the end 
#  it just boils down to whether or not you want to / need to 
#  apply list comprehensions; for the sake of simplicity i'm just 
#  looking for the first worksheet template received:
worksheet_template_id = models.execute_kw(db, uid, password, 'worksheet.template', 'search', [[['id', '=', tasks[0].get('worksheet_template_id')[0]]]])
print(f'worksheet_template_id: {worksheet_template_id}')
# result:
#  worksheet_template_id: [1]

# read the worksheet template data and receive 'fields' - here 
#  we're interested in the model_id. this is the model 
#  (ir.model record) that actually holds all the fields defined:
worksheet_templates = models.execute_kw(db, uid, password, 'worksheet.template', 'read', [worksheet_template_id], {'fields': ['model_id']})
print(f'worksheet_templates: {worksheet_templates}')
# result:
#  worksheet_templates: [{'id': 1, 'model_id': 
#                        [714, 'Default Worksheet']}]

# search for the fields assigned to that model:
worksheet_template_field_ids = models.execute_kw(db, uid, password, 'ir.model.fields', 'search', [[['model_id', '=', worksheet_templates[0].get('model_id')[0]]]])
print(f'worksheet_template_field_ids: {worksheet_template_field_ids}')
# result:
#  worksheet_template_field_ids: [9922, 9921, 9920, 9919, 9924, 
#                                 9923, 9917, 9918, 9916, 12565]

# read the fields data and receive 'fields' - this is just a 
#  reduced example returning only the name of the fields. 
#  highly depends on what information of the field definition 
#  your're interested in:
worksheet_template_fields = models.execute_kw(db, uid, password, 'ir.model.fields', 'read', [worksheet_template_field_ids], {'fields': ['name']})
print(f'worksheet_template_fields: {worksheet_template_fields}')
# result:
#  worksheet_template_fields: [{'id': 9922, 'name': 'create_date'}, 
#                              {'id': 9921, 'name': 'create_uid'}, 
#                              {'id': 9920, 'name': 'display_name'}, 
#                              {'id': 9919, 'name': 'id'}, 
#                              {'id': 9924, 'name': 'write_date'}, 
#                              {'id': 9923, 'name': 'write_uid'}, 
#                              {'id': 9917, 'name': 'x_comments'}, 
#                              {'id': 9918, 'name': 'x_name'}, 
#                              {'id': 9916, 'name': 'x_project_task_id'}, 
#                              {'id': 12565, 'name': 'x_studio_a_field'}]

# now, since we know the worksheet template and the task, we 
#  can search for the actually filled up worksheet; again, 
#  limit the search if and as necessary:
filled_worksheet_ids = models.execute_kw(db, uid, password, 'x_project_task_worksheet_template_1', 'search', [[['x_project_task_id', '=', tasks[0].get('id')]]])
print(filled_worksheet_ids: {filled_worksheet_ids}')
# result:
#  filled_worksheet_ids: [1]

# finally, fetch the user input for the worksheet:
worksheet_field_values = models.execute_kw(db, uid, password, 'x_project_task_worksheet_template_1', 'read', [filled_worksheet_ids])
print(f'worksheet_field_values: {worksheet_field_values}')
# result:
#  worksheet_field_value_ids: [{'id': 1, 'display_name': 
#                              'S00001 - Installation', 
#                              'create_uid': [2, 'Administrator'], 
#                              'create_date': '2025-06-23 21:20:13', 
#                              'write_uid': [2, 'Administrator'], 
#                              'write_date': '2025-06-23 21:20:13', 
#                              'x_studio_a_field': 'a user input',
#                              'x_project_task_id': [
#                                3, 'S00001 - Installation'], 
#                              'x_comments': '<p>some random comment
#                                entered in the worksheet</p>', 
#                              'x_name': 'S00001 - Installation'}]

Please note that this is an example and not a production-ready setup. It is supposed to showcases how worksheet data is linked to a task.
You definitely want to make sure that errors, missing or empty values/records etc. are handled appropriately (and double-check in case I've mixed up a id with a template-id).

As a summary:

1. get the Worksheet Template for the Project Task
2. find the actual model and fields defining the Worksheet Template
3. get the user input from the worksheet