I’m feeling the OPs pain too lately.
I enjoy a run or a ride when I find time and enthusiasm, but that’s not even every week.
A couple of thoughts:
I like trail running for the gentleness on my body (compared to pavements), but even when I’m fit I feel like an hour or two gives time to get dressed, do the run, stretch and shower - and feel I’ve done something. When I’m back on the bike it’s different, but I still feel stronger for having done the running.
Would the 100 push-ups challenge fit in an evening when the sofa beckons? Then it’s easier to swap to something longer, on the basis that it’s easier to do some exercise when you’re already doing some.
Does having a goal, an event to aim at or a number, work for you?