Can you pull the numbers on your engine and confirm whether it is HST or not?
That model number seems to be grey, which means it is a mixed parts tractor. Likely the chassis and engine originally belonged to different tractors.
Mainly what need to be determined is if you have a HST transmission, single, or two stage clutch. It seems your tractor could be around 40-50hp, so all options are in the table.
If it's a single or dual stage clutch and it's not a linkage issue, then it seems like you may need to inspect your clutch fork and plate. However, that would only be considered after attempting to readjust your clutch linkage first. Having zero freeplay seems like someone may have already messed around with it, there should be a small amount.