Yep that's the one. I'd been able to leave it, but with the whole WFH thing work IT said I needed to update my MacBook fully. Quite a few games unplayable now. Was midway through a replay of Deus Ex: Human Revolution but can't play that anymore either which is a shame.
Is this Mojave > Catalina? I downgraded to Mojave after I found a bunch of stuff stopped working, might be worth giving that a shot.