Forearm plank, side bridge, bird-dog, dead bug.
This video is a meta-analysis of the best rehab exercises for the glute muscles: https://www.youtube.com/watch?v=EgWSsaC3UJk
This page has pictures of the above mentioned PT exercises: https://mikereinold.com/5-common-core-exercise-mistakes-and-...
I recently did PT for lower back stuff mostly related to sitting for long periods.
I went from constant “3-4” level pain to “0-1” pain. I’m still working on strengthening, and re-injured my back moving something heavy, but PT was a game changer.
A lot of stretching like the above video shows, as well as working on posture, sleeping position, as well as just overall education on how my muscles work and what to do when I feel them tighten up or feel an area swelling up.
It’s mostly simple stuff but requires habit changes and can be time consuming so you have to fit it into regular routines. Stretching before/after bed, while you brush teeth, etc.
You look weird randomly stretching on a stair while you stir your tea, but it can make a big difference.
Among the many other things I had hammered into me about health when I was a kid in the late 1980s and 1990s that I've come to reject is the incessant hammerbeat about aerobics, aerobics, aerobics. I think the evidence is that the average person is better off with a lot more strength training, which will incidentally train you on some aerobics, and if you feel like occasionally folding some aerobics in, hey, go for it. They're not bad or anything. But they ought to be considered a specialist training, like working out legs specifically for biking, not a default that everybody do. Strength training is a default everybody should work on. Strength training isn't so you can lift 300 pounds when you help your friend move... it because it makes everything work better. You sleep better. Your back hurts less. You fall less. You build a better base for aging.
your shoulders will shrug and round forwards, which will limit your range of motion over time. any stretch that retracts the scapula should help; also if you do any exercise like a row, make sure to focus on really pinching your scapula together.
your core muscles will weaken, leaving your spine more vulnerable to injury. "hunched forward" will become your default posture which exacerbates this further. your spine is actually really strong when it is aligned properly, but you need good core strength to do this. doing a "hollow body" pose and your basic plank are good ways to strengthen these muscles (overarching your spine in either direction is a problem).
Edit: You probably also should focus on core work too. Try some forearm planks to start.
I'd say anything that engages the core (superman, plank variations) and activates the upper back (YTWL's) would be good choices, ideally substituted with some stretches or mobility work