when apotheosis is installed, the mod won't work because apotheosis implements it's own anvil and gets rid of the normal one.

?

Apotheosis 1.16.5 4.8.9A0.

when i craft an anvil the mod tooltip is apotheosis

You're not looking at HWYLA, are you?

Because it's not actually showing the block here, but the block entity. (Which is just a technicality of Apotheosis; it adds a block entity to the otherwise vanilla anvil so it can store the anvil enchantments the mod adds.)

But that's not important at all, Tax Free Levels doesn't care about blocks or block entities, it only cares about the anvil screen (or rather the server-side handler of it) and that isn't being replaced at all.

From my testing there's absolutely no incompatibility with Tax Free Levels.
The cost is flattened and renaming items costs 1 level as expected.

So I'm not sure why you're saying the mod "won't work", have you actually tested it?

If you still think it's not working, you can test this yourself:
Go in a creative world, give yourself 1000 levels, a sword and bunch of Sharpness 1 books, then turn off creative mode and combine them all.
You should see that all that combining will barely make a dent in the 1000 levels you have, even if the level cost says something ludicrous like 93 levels.
If you put in only the expensive sword and try to rename it, the cost should always show up as just 1.
And that's it, that's the mod.

If it actually doesn't work, it could still be an incompatibility with yet another mod, in which case you can upload the latest.log file from the logs folder in your Minecraft instance to https://mclo.gs/ and send me a link so I can have a look at what mods and versions specifically you are using.

No, the mod is clearly working!

You have 6 levels and 4 notches on the XP bar and after paying the 5 anvil levels you are left with 1 level and 8 notches.

So you paid 5 levels but gained back 4 notches, in other words, you got a tax return.
(In Vanilla, the XP bar never moves when using the anvil and those 4 notches of XP would thus be gone.)
Not to mention that renaming that sword does show it costing 1 level as intended.

I'm not sure what you expect this mod to do, but your video demonstrates it fully working.

What the mod does is it takes the level cost that you see in the anvil or enchanting table and turns it into an XP cost, which means that you always pay the same amount of XP, regardless of how high the player level is.
E.g. you'll always pay 55 XP when your anvil says 5 levels.

You can usually only notice the effects of this mod when your player level is very high (like 40+), because the higher it is, the more worth a single level is in terms of XP.
(That's why I suggested setting your player level to 1000, so you could really see your player level barely change.)

For small levels as seen in your video there's not much of a difference to Vanilla - but there's still a slight difference.

i tried reproducing the issue with only apoth+dep and TFL, the issue still persists smh so it's not a pack issue

i crafted the anvil normally, and there's nothing in regard when i checked the log.

well my bad i thought the mod just turn the level cost into linear xp, not even right with that i just understood it differently, not wasting more of ur time so thx.