Why not fix the template update file instead? It is only stated that it is now J!4 compatible but nothing was done to the template file or the update was not properly implemented.
I had to copy html/mod_menu/default.php from another template to replace that of the Travelia template with said issue and was able to get the site to load.
I also copied the html\com_content\category\blog.php and rating.php e.t.c.
Website seems to be fine for now but I know there are still files that didnt throw errors because I'm yet to use them on the website.
Just fix the Version 2.0.0 template file for Travelia. It was not updated properly for Joomla 4.
Lets know when this is properly done so we can test it out.