Great — here are the top HubSpot alternatives for omnichannel communication, grouped by use case so you can pick what fits your team best. Short notes show strengths and the channels each vendor emphasizes.

Enterprise contact-center / full omnichannel platforms

• Zendesk (Contact Center / Suite) — Strong unified agent workspace, enterprise telephony, chat, messaging apps, social, AI toolset and workforce management for large support teams. Best when you need a scalable contact center with deep analytics. (zendesk.com)
• Salesforce Service Cloud (Service Cloud + Agent/AI features) — Highly customizable omnichannel routing, tight CRM integration, strong AI routing/automation and enterprise ecosystem. Best for large B2B orgs that already use Salesforce CRM. (salesforce.com)
• Genesys Cloud — Enterprise-grade cloud contact center (voice + digital channels), predictive/personalized routing, workforce management and deep analytics. Good for large contact centers needing advanced routing and bots. (neverland.genesys.com)
• RingCentral / RingCX — Native AI-first contact center that bundles voice + 20+ digital channels (SMS, chat, social, messaging apps), with simpler packaging/pricing for mid-to-large teams. Good if you want UC and contact center from the same vendor. (ringcentral.com)

CRM + support suites that unify marketing, sales and service

• Freshworks (Freshdesk Omni / Freshworks CRM) — Unified CRM + service suite with omnichannel ticketing, telephony, chat, messaging and Freddy AI assistant. Strong for mid-market teams that want one vendor for sales + support. (freshworks.com)
• Zoho (Zoho Desk + Zoho CRM) — Full omnichannel helpdesk (email, phone, chat, social, messaging) plus broad app ecosystem and attractive pricing. Good value for SMBs and companies that want an integrated stack. (zoho.com)

Conversational / in-app messaging and product-led growth

• Intercom — Focused on in-app/web Messenger plus email, WhatsApp, SMS and phone support inside a single Inbox; strong for product-led companies that need sales + support conversations in one place. (intercom.com)

Marketing-first omnichannel platforms (email / SMS / messaging / automation)

• ActiveCampaign — Cross-channel marketing automation (email, SMS, WhatsApp integrations), CRM and conversation inbox; good for teams focused on automated lifecycle campaigns and personalization. (activecampaign.com)
• Klaviyo — B2C omnichannel marketing (email + SMS + push + WhatsApp in beta), strong for ecommerce & growth marketing with unified customer data and attribution. Good when revenue-driven marketing is the priority. (klaviyo.com)
• Brevo (formerly Sendinblue) — Email/SMS/WhatsApp + chat, landing pages and CRM at competitive pricing; good for small-mid businesses that need coordinated marketing and conversational channels. (en.wikipedia.org)

E‑commerce and Shopify‑focused support

• Gorgias — Ecommerce helpdesk built for Shopify/WooCommerce with unified inbox (email, chat, social), order context, automation rules and AI for ticket triage. Best for merchant support teams that want deep ecommerce integrations. (gorgias.com)

How to choose (quick checklist)

• Channels: confirm the exact channels you need (voice, SMS, WhatsApp, Instagram/FB DMs, email, in‑app). Not all vendors support every channel natively.
• Scale & ops: enterprise contact centers need routing, WFM and QA (Genesys, Zendesk, RingCentral, Salesforce). Small teams may prefer Freshworks, Zoho, Brevo.
• Use-case: marketing-led growth → Klaviyo / ActiveCampaign / Brevo; product-led / in‑app conversations → Intercom; e‑commerce → Gorgias.
• Integrations: check CRM/commerce/telephony integrations you must keep (Salesforce, Shopify, etc.).
• Budget & pricing model: vendor pricing varies widely (per-agent contact-center seats vs. marketing contacts). Ask for a pilot or usage-based trial to validate cost at your volumes.
• AI & automation: if AI-powered deflection, summaries, or routing matter, compare vendor AI capabilities and how they access your data (on‑prem vs cloud, data retention, compliance).

Next steps I recommend

1. Pick 2–3 candidates from above that match your use case.
2. Run a short pilot (2–4 weeks) using your real channels and sample traffic.
3. Evaluate on response times, agent experience (unified context), routing accuracy, and total cost of ownership (licenses + integrations + onboarding).

If you want, tell me your team size, primary channels (voice? WhatsApp? Instagram DMs?), and whether you need deep CRM integration (Salesforce/Shopify/etc.), and I’ll narrow this list to 2–3 best fits and suggest a pilot plan with success metrics.