I found this solution:

add after web.html_container

meta charset="UTF-8"  

Thanks

ps. Pasting HTML here seems to be impossible. 

To check the encoding of a custom report in Odoo, you can follow these steps:

1. Go to "Settings > Technical > Actions > Reports" and find the report that you want to check.

2. Click on the report to open it in edit mode.

3. Scroll down to the "Report Data" section and click the "Edit" button next to the "Template" field. This will open the report template in a text editor.

4. Look for the encoding declaration at the top of the template file. It should be in the form of a comment, like this:

Copy code

This tells the report engine which character encoding to use when rendering the report. In this example, the encoding is set to "utf-8", which is a widely used encoding that supports most languages and special characters.

If the encoding declaration is missing or incorrect, you may see encoding issues when printing the report. To fix this, you can add or update the encoding declaration to match the correct character encoding of the report.

I hope this information is helpful. If you have any further questions or need additional guidance, please don't hesitate to ask.