Hundreds, if not thousands.
Every homebuilt in the registry is a unique airplane; the builder is allowed to name it whatever they wish. This tends to stymie attempts to automatically count aircraft types. To a computer, a "Smith Lancair 4" is NOT the same as a "Jones Lancair IV", and if you try catalog them, you get a lot of one-count aircraft types.
Here's just the first page of my list of EAB aircraft in 2020. Notice the variety of types, and the different ways they're designated.
N-NUMBER Regyear MFR Name Model Name SERIAL NUMBER MFR MDL CODE YEAR MFR1001A 2019 GUTZMAN CHARLES W FALCO F8 CG3 05660691001W 2019 CANON BRADLEY E RV6 60208 05620P0 20061001X 2019 BRUCE RYAN LANCAIR IVP LIV-459 05626CO 201210026 2019 STEELE GUY P RANS S12XL AIRAILE 01020939 05614K1 200210027 2019 GORDON RONALD A RANS COYOTE S6-ES 1295910ES 05603D0 19961002C 2019 DERREBERRY ROGER G X AIR F 1001 059006Q 200510039 2019 GRADY WILLIAM T RV-6 22275 05603DY 19971003Z 2019 GOOD G C/GOOD M J KITFOX SERIES 5 S-95060136 05603DZ 19971004Z 2019 HILAND SPORT MS-2 RGH-1 05601NB 19631005 2019 JAMES SNIDER SUPERSTOL-XL JA478-12-15 05638F6 201910059 2019 LONG DANNY P CHALLENGER II LSS CH2-0507-LSS-0130 05627TK 20091005C 2019 MCNEILLY JAMES T LITTLE WING 3 01 05614K3 200510066 2019 CREIGHTON G DEWAYNE FLIGHTSTAR IISC 324 05611Z0 20011006Q 2019 PRISELAC SKYBOLT PS-1 0565572 19791007 2019 BOWERS R J/BOARDMAN D A III MURPHY MOOSE 130 05617KU 20051007P 2019 BRYAN COURTNEY PHOENIX SL 101 05613TP 19861007Y 2019 LOBERGER JIM QUICKIE Q2 2202 05645QW1008Z 2019 PSOTA MINIPLANE 1 83501JH 196110091 2019 HENDRICKSON CARL R CHALLENGER II CH2-0803-CW-2358 056203C 20071009G 2019 LEE JIM R CURTISS ROBIN 1 05614K4 20031009Z 2019 WHITTMAN TAILWIND W-8 DG1 97902YS 1963100BU 2019 DORNIER BU 133 19 2999006 1997100C 2019 WRIGHT BEAUMONT B LANCAIR IV P LIV-032 056064Q 2001100CD 2019 HOWELL CHARLES N COZY 183 05616GT 1994100CS 2019 SCURLOCK DONALD CRAIG CHALLENGER II CH204951324 05902GY 2007
This means each type needs its own search filters to not only find types that match, but to weed out types that DON'T match but have similar names. DonN's search for Wittman W10s is a good example...it got 103 hits for Wittman W10s, but also a batch of hits for Agusta AW109SPs (W10 buried in the name), DJI SW 1000 drones, Virus SW100s, etc.
I'm guessing Don eliminated them manually...easy enough to do, with a one-time ~120-row result. Not so easy when you're trying to find the results for ~60 different aircraft types, and you rerun the same search in January of each year!
Developing new filters, especially for rarer airplanes, is an adventure. Search the database for "Dyke Delta"? 13 hits. But then I notice that many owners use variations of "JD-2" as a model number. Add that to the search terms, and pow...three more hits.
But one is a Stewart JD2FF. Is that a Dyke? Looking online, no: It's a Foo Fighter. So modify the filters so the plane is excluded.
So...15 Dyke Deltas in the 2020 registry. But three are not listed as having Experimental Amateur-Built certification. So the official number, per my original table, would be thirteen.
It's actually kind of fun to do, a bit of detective work. But it's NOT fun if you're trying to chase down dozens of rarer types with awkward type names. So I go for the lower-hanging fruit; aircraft with many examples, or classics with unique names like the Volksplane.
The advantage is, the filters get saved and copied from year to year and don't have to be re-developed. And I've got the system automated on my PC; it takes me only 3 mouse clicks to invoke all the filters and generate the totals for ~60 homebuilt types.
Ron Wanttaja