HALOT gives 5 cognates for Hebrew BXR, 4 of which have heth. The Akkadian
beru that you mention is the only cognate without a heth. So the heth/X in
Hebrew BXR is an integral part of the root.
But XBR and XBRN seem different, as we’ll now see.
2. XBR
As to XBR as a verb, HALOT reports that Aramaic had the same word, but beyond
that, there’s mainly only XBR in Ugaritic. But that’s a noun, “companion,
associate”, in Ugaritic. So the only verb cognate for Hebrew XBR as a verb
per
HALOT seems to be limited to Aramaic. Yet we have previously noted Aramaic
as having both XQR) and )QR) for “citadel”. So an initial heth/X in Aramaic
can be a mere prefix, and may at times be interchangeable with an initial
prosthetic aleph/), not being part of the root.
3. XBRN
Now for the smoking gun.
As to XBRWN/“Hebron”, HALOT reports that the Samaritan Pentateuch M23 has
)ibron. That’s not a heth! It’s an aleph. Is the initial heth/X in “Hebron”
/XBRN a mere prefix, rather than being an integral part of the root, as I
have
argued? If not, and the root of XBRN is XBR (with a heth/X), then why does
the Samaritan Pentateuch leave off the heth/X and have an aleph/)? That
looks
like XQR) vs. )QR) in Aramaic, where the initial letter in Aramaic or Hebrew
(not Akkadian) may be either heth/X or aleph/), and in any event is n-o-t
part of the root.
Once we see “Hebron” being spelled with an initial aleph/), rather than a
heth/X, in the Samaritan Pentateuch, we must ask whether the initial heth/X
in
the normal spelling of XBRN/XBRWN/“Hebron” may be a mere prefix, something in
the nature of a prosthetic aleph, rather than being an integral part of the
root.
Conclusion
The initial heth/X in XBRN/“Hebron” may possibly be a mere prefix. The
linguistic support for XBR as the 3-letter root of XBRN, with heth/X being an
integral part of the root, is much thinner than one might have expected.