Using Falkon web browser You want to hide certain annoying part of a website content.
There is AdBlock built-in and apparently you can not add uBlock Origin and import your custom rules.

Click Falkon menu (hamburger, three lines), Preferences, Extensions, AdBlock, Settings button, Custom Rules.
You can add your own rules, for example copy/paste from other web browser ad blocker plugin custom rules.

Maybe other option is to create new file out of your other browser ad blocker custom rules, save it on the web so it is plain file (Sample plain text file format as an example: https://easylist-downloads.adblockplus.org/easylist.txt)

and import that address into Falkon AdBlock Preferences section mentioned above. (There is Options button and "Add subscription" menu entry).