Here you can find a list of primers on how to port from old versions to the current version. Some versions are lumped together since that particular version never saw much usage.
|From -> To||Primer|
|1.12 -> 1.13/1.14||Primer by williewillus|
|1.14 -> 1.15||Primer by williewillus|
|1.15 -> 1.16||Primer by 50ap5ud5|
|1.16 -> 1.17||Primer by 50ap5ud5|
|1.19.2 -> 1.19.3||Primer by ChampionAsh5357|