Different ways to invest in government bonds:

Directly from the government:
- US bonds: https://www.treasurydirect.gov/marketable-securities/treasury-bonds/
- In Europe works different, usually they carry on some auctions.
Through brokers or managed funds:
- JP Morgan: https://www.jpmorgan.com/insights/investing/bonds
- Vanguard:https://investor.vanguard.com/investor-resources-education/understanding-investment-types/us-treasury-bonds
- Merrill from Bank of America:https://www.merrilledge.com/investing/fixed-income-bonds?cm_mmc=GWM-Edge-Inv-_-Google-PS-_-Invest-In-Treasury-Bonds-_-Brand-Sitelink&ds_rl=8401&ds_rl=8871&gad_source=1&gclid=Cj0KCQjw_-GxBhC1ARIsADGgDjs-fX4Mciqh3lga7JhriU914iSWxZwWduzXm50mogEkuNF8AhdDQq8aAlN4EALw_wcB&gclsrc=aw.ds