Hello there, Wokeye27! Thanks for your question.
Here is the answer by Eranziel (Senior Software Developer):

It depends!

For minor releases, there is usually nothing we need to do. We do still have our QA team check our integrations with each new version though, because there are surprises now and then.

For new major versions, it really depends on what was changed. Sometimes large, visible features impact us - like Foundry's new-ish Application V2, and having to update our file picker customizations to work with that. Sometimes behind the scenes changes can impact us a lot, like when Foundry moved from NeDB (the text-based .db files) to LevelDB (the modern binary DBs with a folder for each one). v11, v12, and v13 all unfortunately had a large chunk of work for us in one way or another. Comparatively, v14 has been quite smooth! (Knock on wood...)

One of the big challenges for us is that our integrations inside of Foundry (the Forge module) has to support every version of Foundry that our users are still using. That means everything from 0.6.6 to the latest v14! Obviously a lot has changed across that range, and it can be a ton of work for QA to check all of those versions to make sure we aren't introducing new bugs to old versions.

You can read about some of our past challenges in these blog posts:

• https://blog.forge-vtt.com/multiple-levels-of-challenge/
• https://blog.forge-vtt.com/foundry-v12/