edubart/otclient (https://github.com/edubart/otclient/wiki)
From site:
Getting started with OTClient is simple! OTClient has multi client/protocol support which means it can run different Tibia protocols/clients (from 7.4 to 10.99). In order to run the different versions all you need to do is this:
- Copy the Tibia.dat and Tibia.spr from your regular Tibia client into
/data/things/<version>/
folder.
For example:
/data/things/871/
this will check for the 8.71 tibia dat/spr files here.
Now you can use that client version by selecting it in the login process: