Shifting career into RPG developer

Hi all and happy holidays, I am a senior software engineer in my mid 40s with about 18 years of experience in the industry, including over 8 in teamlead roles. I mainly worked with C#/.NET, SQL, and Javascript, but I also have a lot of experience in C/C++. I have extensive experience in SQL with SQL Server, Oracle, MySQL, Postgres, SQLite, and even some DB2. I have worked in the financial industry for almost 9 years now. Before the pandemic I was working at an insurance company where all the database and core processes were written in ILE-RPG on iSeries servers. I often needed to login and navigate around files to run queries and did a few very minor changes.

Back then I had an account on pub400. We had a copy of Programming ILE RPG by Jim Buck (3rd or 4th Ed, can't remember) in the office and I read a couple hundred pages into it.

I am thinking of shifting my career to another language for two reasons: 1) I am looking for a field that is less crowded with inexperienced but very cheap "developers". 2) something with opportunities for fully remote work (preferably) as a freelancer. And 3) I really enjoy writing code, but I am tired of the constant pressure and often long hours of web/SaaS/Startups.

I moved to Germany earlier this year and I am learning German. I have about a couple of hours per day I can dedicate to learning whatever I want for the coming 4-6 months.

Do you reckon I could make a career as a remote RPG developer if I spend the next few months learning the language? How is the job market? Any recommendations for certification? Or would building a couple of projects on pub400 be better?