You can if you live in the US! It isn’t particularly expensive either, high explosives are industrial chemistry. A few dollars per kilo. Maybe a little bit more if you want something fancy.

Thanks to movies, people both seriously overestimate and underestimate the capabilities of highly engineered explosive devices, albeit in different dimensions. Generally speaking, sophisticated military targets are not susceptible to generic explosives. A drone with a hundred kilos of explosive will essentially bounce off a lot of targets. An enormous amount of engineering goes into designing an explosive device optimized to defeat that specific target. They use supercomputers to get this stuff right. Exotic engineered explosive devices are unreasonably capable.

TBH, once you realize the insane amount of engineering that goes into it, it kind of takes the fun out of it. A lot of high-leverage research goes into aspects an amateur would never think about.

This is in some ways a blessing. Amateurs with bad intentions almost always fail at the execution because it isn’t something you can learn by reading the Internet.