I think I agree if you don't have someone dedicated to running and maintaining Jenkins. If you have someone at your org that knows what they are doing though, I'd still take Jenkins over GHA any day.

gitlab self hosted though? no outage. i remember equivalent functionality at my last job taking this path

That's significantly more difficult to set up and it cost money. Github's big issues that it's free, Microsoft doesn't want to allocate enough budget to keep the thing running properly.

But for people who either don't pay anything at all or phenomenal amount one 9 of up time is all you need.

If you're actually trying to run a business I guess you can call and gitlab and get an Enterprise contract

That's not just moving actions though, that's moving _everything_ and taking on the maintenance of running it yourself.