- How do you have 20 years of experience yet no portfolio? Surely you must have made small projects along the way (in 20 years), or tools, or scripts?

- Post whatever you have on github, polish it up of course, with proper README files with description, installation, etc -- whatever would be necessary for someone to take a look and reasonable have enough understanding after a minute or two of what it does and how to compile it/run it

- Write a few blog posts on whatever interesting, useful or challenging things you've seen in 20 years (github will also host you site for free (https://www.google.com/search?q=github+blog+free), or use wordpress, medium, etc)

- Contribute to whatever interesting projects you've seen -- start with a bug you've come across that's annoying but conceptually simple to fix, very easy way gateway into contributing to open source

- Link your github, open source contributions, blog on your resume

- Spend the remaining 2.5 to 5.5months grinding leetcode and interview prep material