That's enough upgrades it could cause some issues, but I wouldn't expect it to be a problem with the RAID array itself, mostly applications and configs that don't work anymore because you're jumping 6 years into the future in terms of software versions. Some things like PostgreSQL you have to dump the data out, install the new version and load it back in, so that's one example of something that could break and would be expected to break.

I believe if you just boot the 24.04 installer it'll see the drives right away, they're pretty persistent. But failing that, you can assemble it manually with mdadm --assemble, or you can backup your /etc/mdadm.conf. That should give you some confidence that if something wrong happens with the Ubuntu install it will be easy to reinstall fresh and not lose your array. Just get it mounted readonly in the live ISO so you know how to get your data, and you'll feel a lot safer doing the upgrade.

Boot a live image of the new version and see if it Just Works. It probably will.

If you can, back up the OS (and make sure a restore works) and try the upgrade. If you can just clone the OS to a new drive and upgrade that one so you can swap back, even better. I don't think there's anything like a RAID version upgrade that's going to prevent you from reverting.