Yes, some on steam, others on wine/bottles/lutrix/etc

Never happened to me, I hope they get their shit together and stop that. Ubuntu is the first distro for lots of people who want to leave windows and that does not looks good

I use Ubuntu daily and didn’t seen any add, only during the install they ask once if I want Ubuntu Pro

You can install Orion browser by Kagi and install extensions from Firefox like uBlock Origin