With a fairly low level of electrical knowledge and some wood/metalworking ability, you can also make your own custom board packages for very cheap. Significantly cheaper than Mars Hydro, Spiderfarmer, HLG, etc. for the same quality. And you can fully customize spectrum, power, size, shape, angles, etc.
On Alibaba or AliExpress, you can buy the boards, search for "quantum board". I bought mine from the seller Kingbrite about 5 years ago and they've been great (I don't use them for trees, but have great growth with veggies, flowers, and used to when I grew marijuana too). They make them in various sizes and spectrums. You want boards that use Samsung LEDs ending in H, which are horticultural lights. LM301H is white, LM351H is red, LM301H EVO is white/blue.
You'll need a driver, Mean Well is highly regarded and who I use, but there are others too. The driver size depends on on the total number of boards you use. Typically "constant current" is what you want for LED driving because voltage affects individual LEDs more than current. But constant voltage does work too, it just might mean some LEDs are a little brighter than others. Wiring up the boards to the driver is pretty simple, but the exact method depends on the driver you use. Constant current requires series connection, constant voltage requires parallel. Make sure the driver has enough voltage and current to power all of your boards (for example, if you have 4 boards at 12V and 2A each, you need a constant current driver that puts out at least 48V and 2A; or a constant voltage driver that puts out 12V and 8A).
Then you make a backplate for the boards, 1/4” or less aluminum sheets work well for shedding heat, and they're pretty light. You'll want to stick the boards to the backplate with thermal tape to ensure a thermal connection between the boards and backplate. Making your backplate allows you to really customize the size and shape of the light. You can do a long rectangle, square, L, T, whatever, depending on the area you're putting the plants. It also lets you space the boards out as much as you need to.
If you want the boards at varying angles, heights, or anything else that can't be accomplished by just having an aluminum sheet to which all boards are attached, a custom enclosure can be made using wood or metal. You can also make the light far more aesthetically attractive this way if you're going to have it in a living room or something. If you go this route, you don't need the aluminum backplate, but you do need to make sure there's an inch or 2 gap between the enclosure and the boards if it's wood because wood is not a good conductor of heat. You should cut venting slots into the wood behind the boards too. If you use metal, do the same as the aluminum plate with thermal tape.