I use to

[RandomBasic]

I've been noticing this all over the place: 'I use to like xyz, but now abc'

It is useD to.

I don't know if it's called the past participle, but many people seem to be dropping the 'ed' part of words.

I can't think of other examples now, but I don't understand why they would do this.

[PAFMO]

It's a common mistake although the opposite over-application of the past tense is actually much more common- you even see it in print which has presumably been edited and/or proofread. (I didn't used to like it etc)
I think in the affirmative form the past tense ending is omitted because of two things- the pronunciation- the "d" isn't pronounced as a /d/ but takes the /t/ from the beginning of "to" and also because as a concept it exists only in the past (something which was once the case but isn't now) so even though people are talking about the past, in some ways they don't code it internally as the past and therefore don't add the "d".
I've not seen it written tbf. But I've seen a lot of "didn't used to" and "did you used to"

[RandomBasic]

they don't code it internally as the past

Yes, exactly! That's why I find it odd.

[MissNothing1991]

Irritates me as much as people spelling it draws instead of drawers