You can but the mower will now be 1" lower at the back so requiire a substantial deck adjustment,
You will also loose 1" of maximum cutting height and the mower will go 10% slower in every gear.
Pull the wheel off and dip it in some waater to find out where it is leaking from as changing the tyre will do nothing to stop a leaking valve stem deflating the tyre.
Check the condition of the rim at the bottom of the flange,
If it is not clean and smooth no tubeless tyre will be able to make a seal.
There is a lot of rye grasses around here and the rye grass seeds can make their way under the tyre and cause a leak