Learning grid will help you in the future and will eventually be supported by all modern browsers. IE11 usage is very low these days so is not a great issue if you supply a fallback or simpler layout without going too far overboard.
You can achieve the same layout in flex so you could use @supports and give ie11 a flex layout.
You can forget about floats (other than for floating things or for very simple structures) but your list misses out my favourite layout option and one I have used on hundreds of sites over the last few years and proved to me the most robust of all. The display:table properties are supported right back to IE8 and can produce many solid grid type layouts with ease.
These days I still tend to use display:table but will quite often use flex also. Grid is good but overly complex for simple layouts. The future is definitely grid shaped so it is worthwhile to practice and construct layouts using grid especially if its for your own projects. You should probably concentrate on learning flex first and then grid (or both).
Remember though that even if you use grid you are still going to want to use flex or other layout methods inside the grid sections.