> searching "Arduino" returns entirely knockoff boards for me on the first page
Something to be aware of - there are mainly three classes of Arduino boards in the marketplace:
1. Name-brand Arduinos (ie - those marketed and sold, or resold, that come from Arduino.cc)
2. Knock-off Arduinos
3. Counterfeit Arduinos
Many in the hobby understand what #1 is, and I encourage everyone just getting into the Arduino to purchase an actual Arduino Uno first, just to support the community and to get a solid "reference" product.
Where many get confused, though, is on what the difference is between #2 and #3 products. What is the difference between a "knock-off" and a "counterfeit" Arduino?
Ultimately, it comes down to copyrights and trademarks. Arduino has a specific set of marks, verbiage, colors, and symbol placement that they put on their boards, which are designed to convey the notion that "this is a genuine Arduino board".
Any third-party board that attempts to replicate this design in part or entirety is infringing on that, and should be considered a counterfeit board. This extends somewhat to using the name "Arduino" and especially "Uno"; it has long been a "thing" that if you build a custom Arduino for sale, that Arduino.cc would like you to name it something else, and ideally not include the suffix "-uino" (mainly because it makes no sense from the standpoint of the Italian language, IIRC). Using the name "Uno", IIRC, is also verboten, as it is a protected trademark of Arduino.cc as well.
Beyond that, the Arduino as a device is completely open-source; anyone can take the reference schematic and board designs and start making them in his or her basement and nobody will care - unless you start using those trademarked and copyrighted items/symbols/etc.
So if you see a board like that, try to report it to the community. There are ways to do this on the site to report it directly to Arduino.cc (or there were, last I looked). Alternatively, find a thread about this issue (they are all over the Arduino.cc forums) and post what you know there, or start a new thread if all the old ones are "dead".
So how do you tell a counterfeit from a knockoff? Well - a true knockoff can look identical in shape and placement of parts, but what you really want to look for is the lack of use of those IP protected items already mentioned. Look for boards that aren't colored the same, that don't use the same markings, that are named differently. Look for vendors/sellers of the products who almost seemingly go out of their way to differentiate their products from the actual Arduino boards.
Tons of them are out there, many offer options not available at all on the original Arduino Uno boards (for instance, on the QFP 328 there are extra analog input pins not found on the PDIP version - some boards bring those extra pins out to headers!). You can find boards with extra integrated peripherals, ones that don't follow the Arduino header layout at all, plus specialized products meant for a particular market, but which could be repurposed for your own use if you wanted to (popular examples are the various ATMega-based 3D printer and CNC controller boards available - there are also a few specialty robotics controllers on the market. There used to be, but not so much anymore as things have migrated toward ARM and other embedded controllers - boards that were meant for multi-rotor drones and the like).
You will find boards out there that "skate the line" - they may use similar colors, similar (but not the same) markings or symbols, etc; for those you'll have to use your best judgement and conscience to decide on buying.
Also note that there are certain boards which exist as only knockoff or "counterfeit"; one can even be hesitant about the latter. These are boards that used to be made by Arduino.cc, but have since been stopped. Take for instance, the Arduino Pro Mini:
https://store.arduino.cc/usa/arduino-pro-mini
This is a nice little board that gives you everything of a full-sized Arduino Uno, in a nice little package that can be easily embedded into a project, much like a PDIP IC, without the bulk of a larger Arduino Uno or other offerings (like the Nano) which add options you may not need (ie, USB interface), or the issues involving embedding an ATMega328 directly into your project (not a great argument, I know). Unfortunately, you can't purchase an official version, only knockoffs are available.
Finally, there are also "Arduino" boards that are only available as third-party options; the popular "Lilypad" variant, for instance, or the interesting "ATmega32u4" based USB "stick" style boards that can plug directly into a USB slot, allowing you to develop all kinds of interesting "hacks" (password or token dongles, keyboard loggers, etc - or just a tiny on-the-go dev board for a laptop).