Guitar Pro still supports the tablature export in ASCII format so it should be quite possible to create a fully working tablatures. It doesn't seem there is any other program that could produce ASCII tablatures from GPX projects.
Convert Guitar Pro 6 format to ASCII text characters file.
We found 2 software records in the database related to .gpx to .ascii file format conversion.
Microsoft Windows software - convert gpx to ascii on Windows
Multi-track editor and music composer for guitars
Convert from gpx file format
|Yes, Guitar Pro supports gpx file conversion as a source file type.||Yes||Yes||gpx editor||Yes||No||No||No|
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned gpx to ascii. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
Apple macOS / Mac OS X software - convert gpx to ascii on OS X
Mac version of the popular tablature editor