While Bethesda is currently having “difficulties” with Fallout 76, leave it to the modding community to come through and ease Fallout fans’ collective pain. “Tale of Two Wastelands”, a mod that lets you play Fallout 3 and its DLC in Fallout: New Vegas, and travel between the two worlds with the same character, has had a “total rebuild” in its 3.2 update.
The mod (which you can find more info about it on its FAQ page) allows you to play through both games with the same character, as well as travel between both games worlds via a train station, all in the New Vegas engine. Plus, you get all of the enhancements of the New Vegas engine (such as the companion wheel and weapon mods) to use in Fallout 3.
The mod requires clean installs of both Fallout 3 and New Vegas (along with all of the DLC), and works with both the Steam and GOG versions. It sadly isn’t compatible with some existing mods, but at least the mod’s forums have a section dedicated to finding workarounds.
And speaking of New Vegas, one user frustrated with Bethesda’s less-than-stellar response to the latest issue with the game (the “canvas bag” controversy) decided to take matters into their own hands and create a canvas bag mod for New Vegas.