Can non-tubeless-ready MTB tyres be used to go tubeless? I'm trying to understand whether it's necessary to buy a new tyre marked as tubeless-ready in order to go tubeless on my new MTB.
Initially, I thought that going tubeless simply requires a sealant, tubeless-ready rims (or rims properly prepared with tape) and valves, and furthermore greatly benefits from having an air compressor at hand for easy assembly.
However, upon closer inspection of the description of the bicycle I bought (Decathlon's Rockrider E-ST 900), the following is stated: &quot;TUBELESS READY rims: you will need tubeless tyres, Presta valves, and puncture sealant&quot;.
I didn't expect I would have to purchase new tyres, retailing at ca. EUR 50 each. Is it really necessary to buy tyres marked &quot;tubeless-ready&quot;, or is the above list of requirements (i.e. valves, rims, sealant and an air compressor) sufficient for making tyres tubeless? If so, are there additional comprises or preparations to be made when using ordinary (non-tubeless-ready) tyres?
On a side note, the tyres on the specific bicycle I bought are of the type Taipan Koloss (Hutchinson), 27.5x2.8in, and according to the manufacturer's website these tyres are already marked &quot;tubeless ready&quot;, which introduces additional confusion.
Another note, I noticed there are a few similar questions, but they do not seem to address the need of tubeless-readiness of tyres in particular.
In general:
It is beter to have tubeless ready (TLR) tyres, but the large volume MTB tyres often work well even when not explicitly TLR. It is much less sensitive than road tyres. However, it should not be a supercheap thin model, that obviously would not hold the air. Also, wired models are less likely to seal well.

To your specific bike:
Decathlon does sell some of the bikes with tubeless ready tyres (e.g., the gravel Triban). And it is the case with your bicycle too. If the manufacturer says it is TLR, there is no reason not to believe them. It is also confirmed at the Decathlon page for the tyre https://www.decathlon.co.uk/taipan-kolos-mountain-bike-tyre-275-x-28-id_8511989.html
Most better quality tyres for MTB are TLR, because it is a must these days. MTB really needs tubeless for good performance.