If you've come here, it may be to fix an urgent problem, so let's cover that first. If you've accidentally locked your function row, so that you can't enter numbers, you should be able to fix this with Fn+ctl. Some people say it has to be the left ctl key. LTC's recommendation is a long press on Fn+space, which resets the keyboard. (Although I assume that would lose any macros you've made).
The other common serious problem is to accidentally set it to Mac mode. This can be fixed by Fn+a which sets it back to Windows mode. To put it into Mac mode the key combo is Fn+s.
Some people have been able to fix both the number key problem and the Mac mode problem with Fn+tab. According to the manual, this begins and ends a macro sequence. I've only experienced accidentally setting it to Mac mode which I fixed with the Fn+a combo.
Now that we've hopefully covered any emergencies, let's talk a little more about the keyboard. This isn't a comprehensive review, there are several online, as well as on youtube. This is just to cover a few things that you might want to know without going through a long article or youtube video.
The keyboard is hot-swappable, meaning you can change switches without soldering. It costs around $60 and is surprisingly good for a keyboard of that price.
The switches aren't the best. I replaced my red switches with silent red, but even the stock reds were pretty quiet. The keycaps are ABS, and as it's a 65% keyboard, it's hard to find replacements. LTC recommends, among others, its own 117 lavacaps pudding keycap set. As a 65% has some odd sized keys, LTC says that the 117 key lavacaps pudding keycaps will have keys to fit the non-standard sizes. If one checks around, you can probably find a keycap set for you. One unusual aspect of the stock keycaps is that the top row has the numbers and also the F keys as keycap legends. I haven't seen too many replacement keycaps that do this. In practice, if I need a function key, I just hit Fn + whatever number I want. For example, to use F5 to refresh a web page, I hit Fn key and 5. Using Fn+esc gives you a backtick, the ` key. I sometimes use this in shell scripting. The tilde, ~, is gotten by hitting Fn+shift+esc. Both backtick and tilde are shown on the escape key, possibly hard to find on replacement keycaps though a few 65% boards such as Ducky and Keychron have it on some default configurations. Speaking of Ducky, their One 3 SF can get a tilde with just shift+esc which I find far better.
The tilde is often used in shellscripting, as well as navigation on a Linux or BSD system, but in a terminal, (as opposed to a vi window), I can often get it to appear by just hitting Fn and almost any number key, which is simpler than hitting Fn+shift+esc. The manual doesn't mention most of these key combos. They do explain how to create a macro. There is also, if you use Windows, which I don't, software that can be used to create macros and swap keys.
This page is almost as sparse as the manual, but I hope the reader finds it useful. Again, there are many longer articles and youtube reviews on this keyboard.