I am wondering, whether what I read online makes much sense in regards to exchanges "banning" mixing services.
I tried it and it seems not. I have tried to mix very small amounts through various mixers and used an account on a major exchange to see wheter they will have a problem with it (as they claim) or not.
Fact is no issues after weeks.

I wonder if in 2021, with the level the mixers have reached with delayed payouts etc., it is still possible to detect wheter a UTXO has been created by a mixing transaction or not.

I have no interest in mixing coins but care for analytical reasons only. I (maybe someone does) would not know what heuristic approach would be working where you don't have uncertainty to an extent where it makes no sense to call it information.