That said, if you are earning $100k in Vilnius, then it will be extremely difficult to find a higher-paying employment offer relative to living costs anywhere in the world. Maybe you can make 1.5-2x that if you go to work in finance - but you will most likely need to move to some of the most expensive cities (Zurich, London, etc) in the world.
The typical way of increasing income as a freelancer, after maxing out the hourly rate on your own is to start a development company. Partner with 1-2 freelancer friends, and start taking on bigger projects. Hire a small team of junior developers, and bill out their time as well. Grow. Start taking on fixed-bid mid-sized enterprise and government projects.
But this can be a very tedious and soul-crushing change, especially at the stage where you have only a few junior developers on staff: you will need to move from doing actual development work to reviewing their code, and handling "management and sales".
If that doesn't sound like something for you, perhaps instead consider:
* Moving to somewhere with even lower cost of living than Vilnius. Hell, move to the next beach-front villa somewhere in Asia every 6 months.
* Be more picky about accepting work - optimise for how much fun they seem to be, not only the hourly rate.
Agency - i tried, so far it didn't work. I haven't found a single client who wanted me as an agency. I think it works differently from freelancer sales: you pitch to totally different people in different situations. My Upwork study also included a separate study of agency success, and it was overwhelmingly negative, there are very, very few successful agencies on Upwork, looks like whole agency thing doesn't work there. Of those not in India/Pakistan and thus working for $10/h (something clearly impossible in my case), there is just 1 really successful one, visibly making >$1M a year: https://www.polcode.com/en/ and a few others making $200-$500K a year, but i seriously don't want to go from 1 person business to 20 person business for 2x raise or 200 person business for 5x raise. And i don't believe i can pull it off. This is something completely unrelated to what i do now, i'd be as good trying to switch careers into an opera singer.
Probably a good choice (and a challenging one), would be to build a new freelancer site, targeting better and bigger customers, not the classic freelancer customer which make decisions based on price.
Obviously this site should get onboard top notch developers/freelancers and curate them.
If you are in the top 10 on UpWork currently, then very few people in the world know how to achieve what you have already achieved, much less improve upon it. You can try to look for ways to improve your income further, but most people are not going to know an answer for you.