Well I actually managed to get this to update, by opening super user and clicking on the 3 dots ⇨ upgrade from the apps list. 

However I still can’t update l10n_ch with this odd version number:

l10n_ch - v 13.0.10.0

Local: 13.0.11.0 | Remote: 13.0.11.0 

I get this terrifying message, which to me looks really similar from the one I got from my previously failing updates:

Error:
Odoo Server Error
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/odoo/http.py", line 624, in _handle_exception
    return super(JsonRequest, self)._handle_exception(exception)
  File "/usr/lib/python3/dist-packages/odoo/http.py", line 310, in _handle_exception
    raise pycompat.reraise(type(exception), exception, sys.exc_info()[2])
  File "/usr/lib/python3/dist-packages/odoo/tools/pycompat.py", line 14, in reraise
    raise value
  File "/usr/lib/python3/dist-packages/odoo/http.py", line 669, in dispatch
    result = self._call_function(**self.params)
  File "/usr/lib/python3/dist-packages/odoo/http.py", line 350, in _call_function
    return checked_call(self.db, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/odoo/service/model.py", line 94, in wrapper
    return f(dbname, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/odoo/http.py", line 339, in checked_call
    result = self.endpoint(*a, **kw)
  File "/usr/lib/python3/dist-packages/odoo/http.py", line 915, in __call__
    return self.method(*args, **kw)
  File "/usr/lib/python3/dist-packages/odoo/http.py", line 515, in response_wrap
    response = f(*args, **kw)
  File "/usr/lib/python3/dist-packages/odoo/addons/web/controllers/main.py", line 1322, in call_kw
    return self._call_kw(model, method, args, kwargs)
  File "/usr/lib/python3/dist-packages/odoo/addons/web/controllers/main.py", line 1314, in _call_kw
    return call_kw(request.env[model], method, args, kwargs)
  File "/usr/lib/python3/dist-packages/odoo/api.py", line 387, in call_kw
    result = _call_kw_multi(method, model, args, kwargs)
  File "/usr/lib/python3/dist-packages/odoo/api.py", line 374, in _call_kw_multi
    result = method(recs, *args, **kwargs)
TypeError: button_immediate_upgrade() takes 1 positional argument but 2 were given

Thanks for your help.