What are some better ways to earn money? eg. with high interest rates etc?

Get another job or start a side hustle? It's not that hard to add another 300 or 500 per month with a part time gig at night or on the weekend.

To put that into comparison, another 6k per year would be to increase a 2% return of 100k to 8% return on 100k.

Not so easy. And you need 100k.

Willl need a comparison for ‘better’. If there is high interest rates, you can look at stocks of banks/brokerage or sell your assets. Bond yield is inversely related to interest rate so long term bonds are not very ideal.