Mozilla is unhappy because the use of browser engines other than WebKit will be restricted to the EU, forcing them to develop two different apps.
For an independent browser like Firefox, managing two browsers is not easy, so it can be forgiven that this could be seen as almost harassment.
Also, the fact that the use of browser engines other than WebKit is limited to iOS means that the use of WebKit is still forced on iPadOS, which also increases the effort for Mozilla.
Not a solution.
This not only has a time and effort cost attached to it but selling your used hardware to buy new hardware is always a bad value proposition.
Then sell stonks.
(For legal purposes this is a joke.)