Entry into ICS/OT Cybersecurity

Does anyone know, what is the best practical way to enter ICS/OT Cybersecurity field for a Control system professional ?

I have 20+ experience in hardware and software engineering for DCS, PLC systems but completely new in OT Cybersecurity field.

So, what is the best practical way to do that like the "good training course name", "good certification course" etc. It is purely OT cybersecurity and NOT "IT Cybersecurity"which is very vast.